Office 2010 Uninstall
As far as uninstalling 2010 Beta, it is the program from Hell. I was in the same boat when I went to install the RTM. I'll tell you what I used and it finally worked.
There will be more than one step to this. First you need a couple of files.
1. Ripoutoffice2007.zip (can be found by doing a search on the web)
2. Ms Install cleaner, msicuu2.exe. (can be found by doing a search on the web)
There is another one that you can use if you like. It is named clean2cr.zip also available via the web.
First I ran the uninstall from Win7 it failed just as you mentioned. I then used ripoutoffice2007 it worked on the 2010 Beta. Then I ran the MS Install cleaner. Ir got some more of it.
Wait, you are not done. I went through my directory tree and removed some stray files. Wait, you are not done. In Win7 there is more than one directory with Office entries. So you will have to check everywhere.
Now the final thing I done was regedit and search for Office. Found several entries. Two of which would not delete. But evidently they did not impede the 2010 Install.
If all else fails you can try this mish-mash. Good Luck